Cussler's oldest and best known books are entries in the Dirk Pitt series, adventure novels that all feature the same hero. The first novel in the series was written in 1973, and Cussler released the most recent entry in 2014. In total, there are 23 books in the series. Cussler has also contributed writing to four other series of adventure novels; however, all of these series were co-authored with other authors who regularly write in the thriller or mystery genres.